7. PROJECT SUMMARY This project collaborates with the New York City Department of Health and Mental Hygiene (NYC DOHMH) to develop and test a field-based comprehensive sexual health intervention for HIV-exposed contacts notified by its Partner Services (i.e., HIV contact tracing) program. Individuals reached by PS programs are highest priority for linkage to HIV prevention/care services: 10-20% are newly diagnosed with HIV as a result of PS notification and the remainder are eligible and high priority for PrEP. Because they seek out highest-risk individuals in the field, PS programs have the potential to significantly reduce existing disparities in PrEP uptake and timely HIV care initiation by reaching populations that are currently under-engaged by traditional PrEP or HIV testing programs. The new Partner Services-Sexual Health (PS-SH) intervention offers a comprehensive sexual health package that includes HIV testing, STI testing, ARV/PrEP education and immediate medication start to all individuals receiving contact notification (i.e., being notified of a recent exposure to HIV). NYCDOHMH is collaborating on this research project to enable a scientifically rigorous test of the intervention?s efficacy and produce the highest quality data on implementation dynamics, cost-effectiveness, and affordability to inform dissemination and adaptation of the intervention, should it prove effective. The specific aims are to: (1) Pilot and refine a field-based comprehensive sexual health intervention delivered through the NYC DOHMH Partner Services Program. Under this aim, we will pilot the intervention in five highest prevalence NYC neighborhoods for 6-months (n = ~60), examine feasibility and acceptability, and refine the intervention process and protocols for the trial to test effectiveness at scale. (2) Examine the effectiveness of the Partner Services-Sexual Health (PS-SH) intervention in improving rates of HIV testing, linkage to HIV prevention/care, and PrEP uptake among highest risk contacts recently exposed to HIV. Under this aim, we will conduct a cross-sectional stepped wedge cluster randomized trial in which 12 clusters of NYC neighborhoods are exposed to the intervention sequentially, with three clusters moving from control to intervention every 6 months (n = 1150). Primary outcomes are HIV testing, timely PrEP/ARV uptake, and linkage to PrEP/HIV care. Secondary outcomes are STD testing and receipt of STD treatment (if indicated). (3) Conduct preliminary analyses of economic outcomes, including cost-allocation and affordability to allow other jurisdictions to make decisions about implementation. These analyses will include per-outcome cost-estimates, and will develop a blueprint for economic evaluation of the intervention including incremental cost-effectiveness and budget impact analyses for application locally and nationally. The proposed project is poised to have a significant and sustained impact on the field by: a) addressing a critical gap in the prevention/care continuum to reduce persistent disparities in the epidemic; and b) pioneering a collaborative implementation science approach to accelerate the dissemination of evidence-based practice models across the United States and internationally.